Geology Reference
In-Depth Information
FIGURE 9.1
Change in water-pressure surface, compaction of confining beds, and associated land subsidence. (Original art and
sketch. With the 1975 Burgess edition)
A large part of the compaction (and the surface
subsidence) is due to the behavior of the clayey confin-
ing layers. The amount of compaction or volume
reduction depends partly on the type of clay present in
the confining beds. For example, the clay mineral
montmorillonite (smectite) may contain more water in
its structure and be more porous and compressible
under a given load than clay composed mainly of the
minerals illite or kaolinite. The chemistry of the clays,
the texture of the sediment, and the overburden load
also affect the reduction of volume and therefore the
amount of subsidence.
QUESTIONS (9, PART A)
Refer to Table 9.1 to answer questions 1-5.
1.
The most common types of deposits involved in ground
water-induced subsidence are:
TABLE 9.1 Description of Areas of Major Land Subsidence Due to Groundwater Extraction (modified from Poland,
1970, pp. 11-21)
Depositional
Environment
and Age
Depth Range of
Compacting Beds Below
Land Surface (m)
Maximum
Subsidence
(m)
Area of
Subsidence
(sq. km)
Time of
Principal
Occurrence
Location
?
Japan: Osaka
and Tokyo
Alluvial (?);
Quaternary (?)
10-200 (?)
3-4
1928-1943,
1948-1965+
Mexico: Mexico City
Alluvial and
lacustrine; late
Cenozoic
Chiefly 10-50
8
25+
1938-1968+
Taiwan: Taipei Basin
Alluvial, late
Cenozoic
30-200 (?)
1
100±
7-1966+
?
Arizona: central
Alluvial
and lacustrine (?);
late Cenozoic
100-300+
2.3
1952-1967+
California: Santa Clara
Valley
Alluvial; late
Cenozoic
50-300
4
600
1920-1967+
California: San Joaquin
Valley (three areas)
Alluvial and lacustrine;
late Cenozoic
90-900
9
5,200
1925-1977+
Nevada: Las Vegas
Alluvial; late
Cenozoic
60-300 (?)
1
500
1935-1963+
Texas: Houston-
Galveston area
Fluviatile
and shallow marine;
late Cenozoic
50-600+
1-2
10,000
1943-1964+
Louisiana: Baton
Rouge
Fluviatile and
shallow marine;
Miocene to Holocene
40-900 (?)
0.3
500
1934-1953-
